This xerophytic or drought resistant vegetation has adapted to living in dry conditions by having small, twisted leaves with stomata which only open at night to allow respiration.
Perennials, such as ocotillo, become dormant between the rains. Once all moisture has evaporated from the soil, the plant drops its leaves and temporarily stops growing.
Instead of thorns, the creosote bush relies for protection on a smell and taste that wildlife find unpleasant. Creosote has an extensive double root system -- both radial and deep -- to accumulate water from both surface and ground water.
Cactus, xerophytic adaptations of the rose family, are among the most drought-resistant plants on the planet due to their absence of leaves, shallow root systems, ability to store water in their stems, spines for shade and waxy skin to seal in moisture.
Desert plants must act quickly when heat, moisture and light inform them it's time to bloom. Ephemerals are the sprinters of the plant world, sending flower stalks jetting out in a few days. The peak of this bloom may last for just days or many weeks, depending on the weather and difference in elevation.
Resources and Further Reading Robert G. Bailey (1998), Ecoregions, Springer-Verlag New York Farouk El-Baz et al.,(1982), The Desert Realm, National Geographic Tony Allan & Andrew Warren (1993), Deserts, Mitchell Beazley World Conservation Atlas www.geojuice.org